Capt Lou,thanks  :) for that very detailed response.Phew! It'll take me awhile reading it more than a few times before I get my head around it.

Likewise,Mark,thanks. :)

What puzzled me  :-? was that at PHNL I managed a near perfect V/L G/S auto-land hitting the threshold at the right place,bags of room for the roll-out,and yet,at KJFK,same technique and I was landing a bit too far.But as has been explained,at that particular Rwy,the threshold is set farther ahead.

Let's see what happens at EGLL. : ::)